用于储氢材料的碳/掺杂碳气凝胶研究

通过溶胶凝胶工艺,以间苯二酚和甲醛为原料,采用常压干燥法制备有机气凝胶和金属掺杂有机气凝胶;在氮气保护下,经1050℃高温碳化获得碳/掺杂碳气凝胶;通过CO₂活化工艺优化样品微结构、提高其比表面积,获得了比表面积达2582m²/g的碳气凝胶样品。使用比表面积与孔隙度分析仪、扫描电镜（SEM）、透射电镜（TEM）、X射线衍射仪（XRD）对样品微观结构和气体吸附性能进行表征。通过溶胶 凝胶工艺实现了过渡金属的均匀掺杂,并研究了金属掺杂对碳气凝胶微结构特性的影响。结果表明,适当的金属掺杂可提高样品的比表面积和微孔体积。     

超低密度碳气凝胶的制备与研究

采用溶胶-凝胶技术制备了超低密度的间苯二酚-甲醛(RF)有机气凝胶(10 mg/cm³),将此气凝胶高温碳化,得到了密度只有20 mg/cm³的碳气凝胶,并用扫描电镜、透射电镜、N₂吸附法等表征了低密度碳气凝胶的微观结构、孔特征等性质。研究发现,低密度碳气凝胶是由粒径10～15 nm的碳纳米粒子以单链珍珠链状连接组成的三维网络结构;而这些纳米颗粒是由更小的石墨微晶构成,微孔主要存在于碳纳米颗粒中,比表面积达1 783.7 m²/g。氢吸附测试发现,此低密度碳气凝胶常压下在液氮温度时吸氢量可达4.4%（质量分数）。     

惯性约束聚变靶材料碳气凝胶的制备方法

用溶胶-凝胶法制备出了高RC比(间苯二酚与催化剂的摩尔比)的RF有机气凝胶,通过溶剂替换,成功地实现了常压条件下的干燥工艺.经高温碳化处理,将RF有机气凝胶转化为碳气凝胶,改变RC比和聚合单体的质量百分数,可控制气凝胶的粒径及孔径、密度及比表面积.用扫描电镜(SEM)、BET等方法对其颗粒大小、密度、比表面积及孔径分布等微结构进行了分析测试.制备出的碳气凝胶性能满足惯性约束聚变靶材要求.     

惯性约束聚变靶材料碳气凝胶的制备方法

用溶胶－凝胶法制备出了高RC比（间苯二酚与催化剂的摩尔比）的RF有机气凝胶,通过溶剂替换,成功地实现了常压条件下的干燥工艺。经高温碳化处理,将RF有机气凝胶转化为碳气凝胶,改变RC比和聚合单体的质量百分数,可控制气凝胶的粒径及孔径、密度及比表面积。用扫描电镜（SEM）、BET等方法对其颗粒大小、密度、比表面积及孔径分布等微结构进行了分析测试。制备出的碳气凝胶性能满足惯性约束聚变靶材要求。     

体积法测量储氢量的状态方程研究

体积法是表征储氢量最主要的技术手段之一,状态方程能否真实描述氢气的p-V-T特性是影响测量精度的关键因素。本文基于芶清泉的物理思想,提出了状态方程新模型。从碳气凝胶储氢量测量过程中得到的实验数据出发,分别应用理想气体状态方程、范德华耳斯方程以及状态方程新模型计算间苯二酚-甲醛碳气凝胶在不同温度、压力下的储氢吸附量,分析了造成结果差别的物理原因。结果显示,利用新的气体状态方程,可明显改善体积法测量结果的可信度。     

气凝胶的制备及其在惯性约束聚变实验中的应用

气凝胶是惯性约束聚变(ICF)实验中的一种理想的靶材料.文章介绍SiO2气凝胶、有机和碳气凝胶、二元气凝胶、掺杂SiO2气凝胶和其它几种气凝胶的研制,探讨了气凝胶在ICF相关研究领域的应用.     

碳化硅气凝胶的模板限制反应法制备与特性

提出了一种酸催化制备间苯二酚 甲醛/二氧化硅复合气凝胶的方法,产物经碳化后得到碳/二氧化硅复合气凝胶。利用模板限制的镁热反应法,在低温（700 ℃）下将C/SiO₂气凝胶转化为纳米SiC气凝胶,并讨论了SiC的镁热反应机制。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶红外光谱（FTIR）、拉曼光谱（Raman）和比表面积分析（BET）等测试技术对样品进行了表征。结果表明,产物由立方相SiC纳米晶组成,保留了与原始气凝胶模板相似的微观形貌,表观密度约为130 mg/cm³,比表面积约为230 m²/g。这种模板限制反应法适用于多种碳/过渡金属氧化物复合气凝胶向碳化物纳米泡沫材料的低温转化,将有利于激光惯性约束核聚变实验用靶的应用研究。     

块状氧化铁气凝胶制备初步研究

研究以氯化铁的醇溶液为前驱体、有机路易斯碱为凝胶促进剂,快速制备氧化铁的醇凝胶,再通过CO2超临界干燥工艺得到氧化铁气凝胶。用透射电镜(TEM)对氧化铁气凝胶的微观结构的表征结果表明,气凝胶主要由超细微粒堆积而成。经BET和BJH测试,气凝胶样品的密度为138 mg/cm3时,孔径为97 nm,孔体积为1.97 cm3/g,比表面积为487 m2/g。XRD研究表明,组成氧化铁气凝胶的晶形结构主要为-βFeOOH。     

新型惯性约束聚变靶材料碳气凝胶研制

用溶胶－凝胶法和超临界干燥工艺制备有机气凝胶,经不同碳化温度处理制出具有不同微结构的碳气凝胶用作新型惯性约束聚变靶材料,用差热分析和热失重分析研究碳化过程中有机气凝胶成分变化以优化碳化工艺,Ｘ射线衍射分析不同碳化温度对碳气凝胶微结构的影响,结果表明,碳气凝胶颗粒由内部石墨化丝状物相互交联形成,碳化温度和碳化时间对颗粒内结构影响不大。     

高度定向的碳纳米管阵列的制备

使用99．99％的铝片．在草酸溶液中,通过基于自组织基础上的二次氧化法制备了孔高度有序、六角排列的氧化铝模板,在微米尺寸区域内获得了高度平行的氧化铝纳米孔阵列。利用化学气相沉积技术(CVD),在没有任何过渡金属催化剂的情况下,利用多孔氧化铝模板本身的催化作用,在氧化铝模板孔内成功制备了高度有序的平行碳纳米管阵列,这种碳纳米管阵列可以作为研究离子束沟道传输特性的较理想材料。利用扫描电子显微镜(SEM)和电子背散射衍射(EBSD)等测试手段对铝片、氧化铝模板和碳纳米管的结构进行了表征。讨论了氧化铝模板的形成机制和基于氧化铝模板生长高度定向碳纳米管的条件。     

氧化锡纳米晶气凝胶制备及其表征

介绍一种低体密度、高表面积、具有纳米量级骨架和晶粒尺寸的块状多孔氧化锡(SnO2)气凝胶的制备方法。场发射扫描电子显微镜（FESEM）表明，气凝胶是由大量纳米粒子堆积而成的三维多孔材料。高分辨透射电子显微镜（HRTEM）表明，气凝胶的骨架粒子由平均粒径为2～3nm的纳米微晶构成。N2吸附表明，气凝胶具有较高的比表面积，约为355.65m2/g，通过该方法计算出的气凝胶的骨架颗粒粒径为2.4nm，与HRTEM结果吻合较好。     

ICF用铜基低密度气凝胶靶材料研制

过渡金属基气凝胶是惯性约束聚变实验中靶的候选材料。以无机铜盐CuCl₂的醇溶液为前驱体,采用聚丙烯酸为分散剂,环氧丙烷为凝胶促进剂,通过溶胶-凝胶工艺制备了柱状铜基醇凝胶。铜基醇凝胶经CO2超临界流体干燥后即可得到浅绿色柱状铜基气凝胶靶材料,材料密度为120~150mg/cm³。由扫描电子显微镜对气凝胶的微结构分析可知,该样品呈现由纳米级球形颗粒均匀堆积而成的网络结构。红外光谱、X射线衍射图谱和X射线荧光光谱的结果表明,样品结晶部分的成分主要为斜方晶Cu²⁺₂Cl(OH)₃,而无定形部分的成分为水合氢氧化铜。     

Plasma treatment for enhancement of the sorption capacity of carbon fabric

In this work we carried out an experimental investigation into enhancement of the sorption capacity of carbon fabric using plasma treatment methods.Carbon fabric is based on viscose fiber and is hydrophobic by nature.Enhancement of the fabric sorption capacity is required for its application in medicine.For this purpose,two plasma treatment methods were considered,i.e.atmospheric nonequilibrium radiofrequency(RF)discharge and a vacuum RF plasma source with an external magnetic field.Samples treated by atmospheric discharge demonstrated aging effects during the first week after treatment.The sorption capacity of samples treated by the RF plasma source was stable over the same period and reached values as high as 0.95.Parameters of the beam created by the vacuum RF plasma source were analyzed and dependences of the fabric sorption capacity and specific surface area on plasma treatment time were investigated.We found that sorption capacity reached its maximum value after 30 min of treatment and did not change significantly if processing was continued,while the specific surface area reached its maximum after 3 min of treatment and quickly decreased after that.It was found that the micropore structure of the fabric remained almost the same during plasma treatment.The volume of mesopores in a unit of the fabric mass(specific volume)doubled during the first 5 min of treatment and returned to initial values after 30 min of treatment.The sorption capacity continued to increase even when the specific surface area decreased after reaching its peak value.This indicates the important role of surface functional groups formed on carbon fibers during plasma treatment.This is consistent with the results of x-ray photoelectron spectroscopy analysis showing changes in surface oxidation during plasma treatment.     

Chemical analysis of fuel crud obtained from Korean nuclear power plants

Crud samples were obtained from two different kinds of used fuels in PWRs. The constituent elements were analysed according to the shapes of crud particles by SEM and EPMA. The principal elements of octahedral crystal particles were identified as Ni and Fe, where the ratio (Fe/Ni) was approximately 2. The major element of the observed needle-like structures was determined to be Ni. In addition, Zr composed the main element of particles shaped like broken fragments sized at 10-50 μm in diameter. The round particles less than 20 μm in diameter were identified as Si-containing compounds. We also found the Zn element in a series of fuel crud samples obtained from a plant. Zn was mainly detected in the hard crud, inner layer of crud, but not on the surface of crud. It was observed that there is an inverse relationship between the Ni and Zn contents in the hard crud.     

SiO2气凝胶常压制备、表面结构与吸附性质

采用溶胶-凝胶技术,以多聚硅（E-40）为源,通过表面修饰工艺,在常压条件下制备了SiO2气凝胶.采用扫描电镜、13C和29Si核磁共振谱以及孔径分布仪对SiO2气凝胶的微结构进行了表征,并用微量电子真空吸附天平对SiO2气凝胶的吸附特性进行了研究.结果表明：SiO2气凝胶具有纳米多孔结构、较好的疏水和亲水可调性,是一种极好的高吸附材料.     

异氰酸酯增强二氧化硅气凝胶的力学性能

采用有机无机复合的方式,制得异氰酸酯增强的SiO2气凝胶。将硅酸甲酯(TMOS)、甲基三甲氧基硅烷(MTMS)、3-氨丙基三乙氧基硅烷(APTES)配成混合硅源,经水解缩聚后形成凝胶,老化后浸泡在含六亚甲基二异氰酸酯单体(HDI)的乙腈溶液中,最后经CO₂超临界干燥,获得了具有良好机械性能的SiO₂气凝胶。制备过程中引入的MTMS增加了凝胶与有机物间的浸润性,与使用有机物低聚体相比,使用单体可使有机物更易进入凝胶网络,反应更充分,形成纳米尺度更均匀的复合气凝胶。复合后的气凝胶密度为330 mg/cm³、比表面积为446.3 m²/g、热导率为0.068 W•m^-1•K^-1,该气凝胶良好的力学性能(压缩强度为19.96 MPa、压缩模量为82.37 MPa)使气凝胶的机械加工成为可能。     

Void fraction and effective thermal conductivity of binary particulate bed

In many industrial processes, solid particles of different sizes are mixed in different volume or mass fractions for various applications, primarily to reduce void volume or to increase the density of the mixture. A few of these processes include; production of high density ceramics, mortar, concrete, graphite, bricks and carbon blocks. Experiments were carried out with alumina and lithium titanate pebbles (size ≥ 1 mm) and particles (size < 1 mm) of different sizes and volume fractions in cylindrical and rectangular vessels to study the variation of void fraction with volume fraction of component pebbles and with large pebble to small pebble or pebble to particle size ratio. It was observed that the variation of void fraction with volume fraction of smaller pebbles or particles is ‘V-shaped’. Thus there exists a minimum void fraction and two different volume fractions of smaller pebbles or particles which can give same void fraction. The effect of void fraction on the effective thermal conductivity of binary bed of lithium titanate and alumina pebbles and particles of different sizes and volume fractions was investigated. From the experimental results it was found that the binary particulate bed has higher effective thermal conductivity that that of a unary particulate bed. Effective thermal conductivity of binary particulate bed is the maximum when its void fraction is the minimum. The binary particulate bed with less volume fraction of small particles has higher conductivity than that of the binary bed of higher volume fraction of small particles and having same void fraction. This is due to the fact that with increase in volume fraction of small pebbles or particles, the number of small-to-small and large-to-small pebbles and or particles contact point increases resulting in higher resistance to heat transfers. The experimental details and results are discussed in this paper.